Many containers, such as cartons, boxes or other less rigid containers, are constructed from paper-based materials and include open ends each having a plurality of flaps. Typically, the flaps at each end include a pair of opposed major flaps and a pair of opposed minor flaps. The containers are usually folded from a flat condition into an erected condition, after which a desired product may be introduced into the container. The flaps are then folded and connected together, typically using an adhesive, to close the opposite ends of the container. The minor flaps are folded down first and the major flaps are folded down next and sealed to upper surfaces of the minor flaps using adhesive.
Particulate products, such as granulated or powdered products, require packaging that prevents leakage of the product during shipment and storage. Plastic liners may be used inside the container for this purpose, however, such liners increase packaging costs. To reduce costs, linerless siftproof containers and sealing methods have been developed for storing and shipping particulate products. The end flaps of these siftproof containers must be tightly sealed in a manner that prevents the contents from sifting out between the flaps and which likewise prevents infestation by insects through gaps between the flaps. In the past, all of the flaps have received adhesive deposits in the form of intermittent or continuous adhesive beads to ensure that the seams between the various flaps are sealed in a siftproof manner.
As the development of siftproof containers has progressed, certain problems have been addressed relative to siftproof seal integrity and costs associated with the adhesive and the paper construction products.
For example, embossments have been used on the various flaps to provide opposed surfaces lying in close relation such that the gap between the flaps does not need to be filled with as much adhesive. Other siftproof containers have been configured to include a modified first major flap that enables direct contact between embossed portions of the minor flaps and a corresponding embossed portion of the second major flap. While these improvements have helped in some regards, modifying containers in these manners can also add expense and some containers cannot have embossed or otherwise modified flaps.
Other problems in this art relate to the need for a large of number of adhesive dispensers, or adhesive dispensing nozzles, necessary to place the corresponding number of beads on the container flaps extending in the conveying path of the containers. The increased complexity of the dispensing system increases costs and complicates changeover procedures. In this latter regard, for containers of different configurations and/or sizes, dispensing guns must be removed or added, or nozzles must be removed and plugged or added to accommodate the new configuration or container size.
Despite the various developments in the area of siftproof containers, improvements are still needed to maintain siftproof seal integrity while reducing adhesive requirements and general manufacturing costs. In this regard, the use of continuous adhesive sealing beads as opposed to a number of intermittent short and long beads only extending parallel to the conveying path requires much less adhesive and lower manufacturing equipment and changeover costs due to the lower number of necessary adhesive guns. However, applying a continuous adhesive bead in a direction generally perpendicular to the conveying path during high-speed packaging operations has been a troublesome problem. Many packaging lines are designed to move at a rate of approximately 400-500 ft./min. or above and, at these high speeds, applying accurate beads of adhesive perpendicular to the direction of the conveying path has been a problem inadequately addressed by prior siftproof packaging systems. With the prior art high-speed siftproof packaging methods, beads of adhesive have been applied only in the direction of the conveying path in order to deal with this problem. This results in the use of much more adhesive than necessary to create a siftproof pattern and necessitates the use of multiple side-by-side adhesive dispensing guns and/or nozzles mounted adjacent the conveying path.
To solve these and other problems in the art, it would be desirable to provide a method of applying a siftproof pattern of adhesive to the major and minor flaps of a container while using less adhesive and a lower number of adhesive dispensing components while still maintaining a high production rate in a high speed packaging operation.